This invention relates to the field of telecommunications, and more particularly to a TDM switching system and ASIC complex.
Many telecommunications devices include backplanes for transmitting digital information between components of the devices. For example, a telecommunications switching system might include a backplane for transmitting digital data representing voice signals between cards associated with incoming and outgoing ports. A switching system would also include a switching mechanism to associate incoming data received at an incoming port with an appropriate outgoing port and to route the incoming data to the outgoing port. Within a time-division multiplexing (TDM) switching system, this switching mechanism must receive the incoming data for each time slot, determine the outgoing port for the data for each time slot, and route the data for each time slot to the appropriate outgoing port. Since each time slot may be associated with a corresponding call between persons, computers, or other entities, successful operation of the system in many instances depends on the ability of the switching mechanism to accomplish these goals with tremendous accuracy and speed while meeting the capacity requirements placed on the system.
As the telecommunications industry continues to dominate the growth of the global economy, meeting the accuracy, speed, and capacity requirements placed on a switching system, while reducing to the extent practicable the footprint, manufacturing cost, and power consumption of the switching mechanism itself, becomes increasingly important. However, prior switching mechanisms and techniques are often inadequate to satisfy these needs, at least partially because of the many hardware components and associated circuitry typically required for their implementation. Since each additional component associated with a switching mechanism in general adds to its footprint, manufacturing cost, and power consumption, previous techniques involving relatively large number of such components become less desirable as switching systems become smaller and port density increases. Previous switching mechanisms and techniques do not adequately integrate the functionalities associated with TDM switching and do not fully realize the many technical advancements associated with design and fabrication of application-specific integrated circuits (ASIC). These and other deficiencies become particularly apparent when previous mechanisms and techniques are incorporated into high availability backplane environments of modern TDM switching systems.
According to the present invention, the disadvantages and problems associated with TDM switching systems have been substantially reduced or eliminated.
According to one embodiment of the present invention, a system for switching data between a plurality of network interfaces includes a backplane and multiple cards coupled to the backplane. Each card includes multiple ASIC devices. Each ASIC device is associated with a subset of the network interfaces and capable of switching data from an associated incoming network interface for communication to an outgoing network interface. At least one ASIC device on a particular card is an internally switching ASIC device capable of communicating switched data to an outgoing network interface also associated with the card. Remaining ASIC devices on the card are externally switching ASIC devices each capable of communicating switched data to one or more other cards, using the backplane, for communication to one or more outgoing network interfaces associated with the other cards.
In another embodiment, an ASIC device includes a first RAM that stores a data processing code for each of multiple first time slots, each code able to combine with corresponding data from the first bus to specify a previously stored data processing operation. A second RAM receives the combined data and code for each first time slot and applies the specified operation for each first time slot to generate modified data for each first time slot. A third RAM stores information specifying a second time slot to correspond to each first time slot and communicates the information for each second time slot as an address. A fourth RAM that includes at least first and second portions stores the modified data for a previous frame in the first portion and the modified data for a current frame in the second portion, locates the modified data for each first time slot of the previous frame according to the address, and communicates the modified data for each time slot of the previous frame from the first portion to the second bus in the corresponding second time slot while the modified data for the current frame is being stored.
The present invention provide a number of important technical advantages over prior switching systems and techniques. The present invention provides a switching system that includes multiple ASIC devices on each network interface card, at least one of which allows data to be switched from an associated incoming network interface to an outgoing network interface associated with the same card. Remaining ASIC devices allow data to be switched from an associated incoming network interface to outgoing network interfaces associated with one or more other cards in the system. Using this approach, the present invention allows for increased scalability and port density while reducing manufacturing cost and, at least in one embodiment, taking full advantage of ASIC devices designed and fabricated specifically for TDM switching according to the present invention.
The ASIC device of the present invention provides TDM switching capabilities without the many hardware components and associated circuitry typically required for previous TDM switching architectures. The ASIC device provides speed, accuracy, and reliability suitable for high availability backplane environments with reduced footprint, manufacturing cost, power consumption, and other undesirable characteristics. These benefits become increasingly important as port density increases, making the present invention even more desirable for incorporation in modern TDM switching systems. Moreover, the ASIC device of the present invention provides enhanced data processing, gain/law conversion for example, on a per call basis using a statically programmed look-up table and dynamically programmed codes to specify operations stored in the look-up table. The present invention preserves data integrity during switching operations using a triple bucket RAM and associated write and read strategies, detects faults in the data path, supports multiple serial data bus standards, and provides a host of other benefits. Many of these benefits may be particularly apparent in a high availability backplane environment.